Electric control apparatus for auger type ice making machine

ABSTRACT

When an upper limit float switch Fu is closed after a lower limit float switch Fl is closed according to a rise of the level of water in a water tank 60, a solenoid water valve WV is closed and power supply to an electric motor for driving an auger 40 and a compressor connected to an evaporator 30 is then allowed. When the lower limit float switch Fl is opened, the solenoid water valve WV is opened and power supply to the electric motor and compressor is cut off. When the lower limit float switch Fl is opened, a time set longer by a predetermined time than the time for the water level in the water tank 60 to reach the upper limit from the lower limit is measured. When the lower limit float switch Fl is kept open due to suspension of water supply, the solenoid water valve WV is closed in response to the completion of measurement of the time. This can suppress power consumption of the solenoid water valve WV.

TECHNICAL FIELD

The present invention relates to an auger type ice making machine, and,more particularly, to an electric control apparatus which automaticallycontrols water supply to an evaporator housing of the auger type icemaking machine and the ice making operation of this ice making machinein accordance with the level of water in a water tank connected to theevaporator housing.

BACKGROUND ART

Conventionally, in an auger type ice making machine, as disclosed in,for example, Japanese Utility Model Publication No. 63-10453, a pair ofnormally open type float switches are provided at the top and bottom ofa water tank, so that when the lower float switch is opened, water to beformed into ice is supplied into the water tank from a water source byopening of a solenoid water valve, an ice making operation starts whenboth float switches are closed in accordance with an increase of waterin the water tank to a given quantity to form the water from the watertank into ice crystals and move the ice crystals out of an evaporatorhousing with an auger to sequentially store them as pieces of hard icein a storage bin, the same water supply to the water tank and the icemaking operation are repeated after the lower float switch is opened inaccordance with a decrease of water in the water tank.

With the above structure, as long as both float switches properlyfunction, the ice making operation is automatically ensured whensuspension of water supply occurs and water supply is then recovered.When suspension of water supply occurs, however, the lower float switchis opened, holding the solenoid water valve open. For this reason, thelonger the suspension of water supply continues, the greater thewasteful power consumption becomes to keep the solenoid water valveopen.

Meanwhile, there may be such malfunctions that the individual floatswitches are disabled to be opened or closed due to dust enteringtogether with water in the water tank or melting of the contacts of eachfloat switch caused by an excessive current flowing therethrough. Inthose malfunctions, if closing of the upper float switch is notpossible, this upper float switch cannot be closed when water in thewater tank increases to a given quantity. The solenoid water valvecannot therefore be closed, so that supply of water in the water tankfrom the water source will continue even after the water tank is filledwith water. As a result, water in the water tank is dischargedwastefully through an overflow pipe and the place where the ice makingmachine is set is flooded with water.

If opening of the upper float switch is not possible, this upper floatswitch cannot be opened even when water in the water tank isinsufficient. The solenoid water valve cannot therefore be opened, sothat ice making operation will continue even when there is insufficientwater in the water tank or insufficient water in the evaporator housing,resulting in over freezing in the evaporator housing. As a result, theamount of circulation of a fluid refrigerant from the evaporator in theevaporator housing to the compressor increases, damaging the componentsof the compressor or the over freezing in the evaporator housing acts asan over load to a driving mechanism through the auger, damaging thecomponents of this driving mechanism.

If closing of the lower float switch is disabled, this lower floatswitch cannot be closed even though the level of water in the water tankis kept proper between the locations of the upper and lower floatswitches. Consequently, water supply to the water tank from the watersource via the solenoid water valve starts even though the proper amountof water is remaining in the water tank. Accordingly, in this case wateris not used for ice making to sufficiently reduce the water for onecycle retained in the water tank, dropping the ratio of use of the waterand shortening the service life of the solenoid water valve due to theincreased frequency of opening/closing actions.

If opening of the lower float switch is disabled, this lower floatswitch cannot be opened even though there is insufficient water in thewater tank. Therefore, ice making operation will continue even whenthere is insufficient water in the evaporator housing, resulting in overfreezing in the evaporator housing. This causes substantially the sameshortcoming as arising in the case where opening of the upper floatswitch is disabled.

Further, with the above-described structure, if a refrigerant leaks froma pipe in a refrigeration circuit having an evaporator or compressor,the evaporator does not show sufficient cooling performance due to aninsufficient refrigerant, making the ice making operation unnecessarilylonger. In some cases, the refrigeration circuit becomes avacuum-operating state due to the refrigerant leakage, so that outsideair is sucked inside, causing a critical damage on the components of thecircuit.

DISCLOSURE OF THE INVENTION

It is therefore a primary object of the present invention to provide anelectric control apparatus for an auger type ice making machine whichcan minimize the power consumption for opening the solenoid water valveupon occurrence of suspension of water supply, and can immediately stopwater supply to the water tank or stop an ice making operation when thefloat switches malfunction or the refrigeration circuit malfunctions dueto leakage of the refrigerant.

This object of the present invention is achieved by an auger type icemaking machine having a water tank for supplying water connected to anevaporator housing incorporating an auger rotatable by an electric motorand having an evaporator provided on an outer wall thereof, the icemaking machine comprising:

a first float switch for detecting the level of water in the water tankand being opened (or closed) when the water level drops to a lowerlimit;

a second float switch for detecting the level of water in the water tankand being closed (or opened) when the water level reaches an upperlimit;

a first control means for, when the first float switch is opened (orclosed), energizing a solenoid water valve connected to the water tankand cutting off power supply to the electric motor and a compressorconnected to the evaporator;

a second control means for, when the second float switch is closed (oropened) after the first float switch is closed (or opened) in accordancewith an increase in the water level, closing the solenoid water valve bydeenergization thereof and then permitting power supply to the electricmotor and the compressor;

a timer means for functioning when the first float switch is opened (orclosed) to start measuring a control time set longer by a predeterminedtime than a time for the level of water in the water tank to reach theupper limit from the lower limit, and stopping functioning upon elapseof the control time; and

a third control means for closing the solenoid water valve bydeenergization in response to functional stop of the timer means whenthe first float switch is kept opened (or closed) due to suspension ofwater supply.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partly cutaway view of an ice making machine assemblyaccording to one embodiment of the present invention;

FIG. 2 is a circuit diagram of a refrigeration circuit of the ice makingmachine;

FIG. 3 is an electric control circuit diagram of the ice making machine;

FIG. 4 is a detailed circuit diagram of an electronic driving circuit inFIG. 3;

FIG. 5 is a control circuit diagram of essential portions illustrating amodification of this embodiment;

FIG. 6 is a control circuit diagram of essential portions illustratinganother modification of this embodiment;

FIG. 7 is an electric control circuit diagram illustrating anotherembodiment of the present invention;

FIG. 8 is a detailed circuit diagram of essential portions of anelectronic driving circuit of this embodiment;

FIG. 9 is an electric control circuit diagram illustrating amodification of the second embodiment; and

FIG. 10 is a detailed circuit diagram of essential portions of anelectronic driving circuit of this modification.

One embodiment of the present invention will now be described referringto the accompanying drawings. FIGS. 1 through 4 illustrate the generalstructure of an auger type ice making machine to which the presentinvention is applied. This ice making machine comprises a machineassembly B (see FIG. 1), a refrigeration circuit R (see FIG. 2) and acontrol circuit E (see FIGS. 3 and 4) which controls the driving of themachine assembly B and the refrigeration circuit R.

The machine assembly B has a speed reducer 10 which is driven by a motorMg. This speed reducer 10 reduces the rotational speed of the motor Mgby means of a reduction gear mechanism in a casing 11 and transmits thespeed to an output shaft 12 in a vertical cylindrical portion 11a of thecasing 11. An evaporator housing 20 has a lower flange portion 21fastened to the upper end of the vertical cylindrical portion 11a byindividual screws 22, so that it stands upright on the cylindricalportion 11a vertically and coaxially. An evaporator 30 is coaxiallywound around the outer surface of the evaporator housing 20. Theevaporator 30 cools water entering the evaporator housing 20 to form itinto a flake of ice as will be described later, in accordance with acoming refrigerant.

An auger 40 is fitted coaxially rotatable in the evaporator housing 20,and has its lower-end rotary shaft 41 supported unrotatable relativelyto the output shaft 12 in the vertical cylindrical portion of the casing11. The auger 40 sequentially scrapes ice crystals in the evaporatorhousing 20 by means of a helical blade 42 and guides them upward inaccordance with the rotation of the auger 40. In FIG. 2, the referencenumeral 23 denotes an insulation housing.

An extruding head 50 is disposed on the upper-end inner surface of theevaporator housing 20 and a sleeve metal 51 rotatably fitted over anupper-end rotary shaft 43 of the auger 40, and is secured to the top endportion of the evaporator housing 20 by fastening individual screws tosupport the sleeve metal 51 coaxially. The extruding head 50 compressesice moved upward by the auger 40 in a rod, yielding a rod of compressedice. A cutter 53 is fitted coaxially on the upper end portion of theupper-end rotary shaft 43 of the auger 40 to sequentially cut the rod ofcompressed ice from the extruding head 50 and delivers the pieces of icethrough a delivery duct 54 to a storage bin (not shown).

A water tank 60 is supported on the side of the evaporator housing 20 bya proper securing member, as shown in FIG. 1, so that water from a watersource 60a is supplied into the water tank 60 by selective opening of anwater valve WV in the form of a normally closed type solenoid valve,which is disposed in a water supply pipe 61. The water tank 60 is sodesigned as to permit the retained water to flow via a pipe 62 into theevaporator housing 20 through a lower-end opening 24 thereof. In thewater tank 60 a float switch mechanism 70 is suspended from the rightportion of the top wall of the water tank 60, with an overflow pipe 80vertically extending through the left portion of the bottom wall of thewater tank 60 at its upper end portion 81.

The float switch mechanism 70 has a hollow rod 71 made of a nonmagneticmaterial, which is suspended from the right portion of the top wall ofthe water tank 60. A pair of ring stoppers 72 and 73 and a pair of ringstoppers 74 and 75 are coaxially fitted over the outer surface of thehollow rod 71 at the proper intervals from the lower portion of the rod71 to the upper portion. A ring float 76 is fitted loosely over thehollow rod 71 between the stoppers 72 and 73 coaxially and movable inthe vertical direction. A ring float 77 is fitted loosely over thehollow rod 71 between the stoppers 74 and 75 coaxially and movable inthe vertical direction. Ring magnets 76a and 77a are fitted coaxially inthe hollow portions of the floats 76 and 77, respectively. In the hollowportion of the hollow rod 71, normally open type reed switches 78 and 79are buried in association with the stoppers 73 and 75. The reed switch78 constitutes a normally open type lower limit float switch Fl togetherwith the float 76, while the reed switch 79 constitutes a normally opentype upper limit float switch Fu together with the float 77.

Thus, the reed switch 78 opens responsive to seating of the float 76 onthe stopper 72, which means that the lower limit float switch Fl opens.When the level of water in the water tank 50 reaches a lower limit levelLl, the reed switch 78 is closed by the magnet 76a of the float 76floating at the lower limit level Ll. This closes the lower limit floatswitch Fl. The reed switch 79 opens responsive to seating of the float77 on the stopper 74, thus opening the upper limit float switch Fu. Whenthe level of water in the water tank 50 reaches an upper limit level Lu,the reed switch 79 is closed by the magnet 77a of the float 77 floatingat the upper limit level Lu. As water supply to the water tank 60 iscompleted, the upper limit float switch Fu is closed. The overflow pipe80 discharges excess water outside when the water level in the watertank 50 exceeds the upper limit level Lu.

Referring now to FIG. 2, the structure of the refrigeration circuit Rwill be explained. A compressor 90 is driven by a compressor motor Mc(see FIG. 3) to suck a refrigerant from the evaporator 30 through a pipeP1 to compress it, and allows the refrigerant as a compressedrefrigerant with high temperature and high pressure to flow into acondenser 100 via a pipe P2. The condenser 100 condenses the comingcompressed refrigerant and causes it to pass via a pipe P3 to a receiver110 in a cooling action of a cooling fan 100a. The cooling fan 100a isdriven by a fan motor Mf (see FIG. 3). The receiver 110 performsgas-liquid separation of the received condensed refrigerant and causesonly the liquid component to flow as a circulation refrigerant via apipe P4 to an expansion valve 120. The expansion valve 120 expands thereceived refrigerant and permits it to flow into the evaporator 30 via apipe P5.

The control circuit E is so designed as to be applied with an AC voltagefrom a commercially available power supply Ps via a circuit breaker ELBbetween common leads L1 and L2. A timer section Tk constitutes a firsttimer together with a normally open type timer switch K. The timersection Tk has one end connected to the common lead L1 throughparallel-connected normally closed type relay switches S1 and U1, and anormally open type relay switch Q1 connected in series to both relayswitches S1 and U1. The timer section Tk has the other end connected tothe common lead L2 via a normally open type relay switch V1.Accordingly, when applied with an AC voltage from both common leads L1and L2 with the individual relay switches Q1, S1, U1 and V1 closed, thetimer section Tk functions to measure a predetermined time Dk. The timerswitch K opens when measuring the predetermined time Dk by the timersection Tk is completed, and is closed in response to cutoff of the ACvoltage from the common leads L1 and L2 to the timer section Tk. Thepredetermined time Dk is set about 90 sec, longer than the sum of thetime to supply water via a water valve WV in the water tank 60 to theupper limit level Lu and the time required to energize a relay coil Ru.

A relay coil Rv constitutes a relay together with the relay switch V1, anormally open type relay switch V2, a normally closed type relay switchV3 and normally open type relay switches V4 and V5. This relay coil Rvhas one end connected to the common lead L2 and the other end connectedto the common lead L1 via the timer switch K, a normally closed typetimer switch M and a parallel circuit of a normally open typeself-recovery type operation switch SW and the normally open type relayswitch V2 and a normally open type relay switch Y1. The relay coil Rv isenergized by temporary closing of the operation switch SW caused byclosing of both timer switches K and M to close the individual relayswitches V1, V2, V4 and V5 and open the relay switch V3 at the sametime, and is self-retained by closing the relay switch V2.

A timer section Tm constitutes a second timer together with the timerswitch M. The timer section Tm has one end connected to the common leadL1 through a normally open type relay switch W1, and has the other endconnected to the common lead L2. Accordingly, when selectively appliedwith an AC voltage from both common leads L1 and L2 via the relay switchW1, the timer section Tm functions to measure a predetermined time Dm.The timer switch M opens upon completion of the time measurement by thetimer section Tm, and is closed in response to cutoff of the AC voltagefrom the common leads L1 and L2 to the timer section Tm caused byopening of the relay switch W1. The predetermined time Dm corresponds tothe maximum value of the sum of the time (about 1 minute) to activatethe compressor 90 after closing of the upper limit float switch Fu, thetime (about 3 minutes) to start forming ice crystals after activation ofthe compressor 90, the time (5 to 15 minutes) for the lower limit floatswitch Fl to be closed after closing of the upper limit float switch Fu,and a predetermined margin time.

A timer section Tn constitutes a third timer together with a normallyopen type timer switch N. This timer section Tn has one end connected tothe common lead L1 through a parallel circuit of the relay switch V3 anda normally open type relay switch Y2, and has the other end connected tothe common lead L2 through a normally open type relay switch Q2.Accordingly, the timer section Tn functions to measure a predeterminedtime Dna when applied with an AC voltage from both common leads L1 andL2 with either the relay switch V3 or Y2 and the relay switch Q2 closed,and measures a predetermined time Dnb upon completion of the measurementof the predetermined time Dna. The timer switch N is kept open while thetimer section Tn measures the predetermined time Dna, and is kept closedwhile the time section Tn measures the predetermined time Dnb. The timerswitch N also opens when the measurement of the predetermined time Dnbis completed. The predetermined time Dna is set to a value between oneto three hours, and the predetermined time Dnb is set to a value between1 to 60 sec.

A relay coil Ry constitutes a relay together with both relay switches Y1and Y2. This relay coil Ry has one end connected to the common lead L1via the timer switch N, and has the other end connected to the commonlead L2 via the relay switch Q2. The relay coil Ry is energized to closeboth relay switches Y1 and Y2 when the timer switch N and relay switchQ2 are both closed. A relay coil Rq constitutes a relay together withthe individual relay switches Q1, Q2 and Q3. This relay coil Rq has oneend connected to the common lead L1 via a normally closed type storedice detector SI, and has the other end connected to the common lead L2.The relay coil Rq is energized to close the individual relay switchesQ1, Q2 and Q3 when the stored ice detector SI is closed. When thequantity of stored ice in the aforementioned storage bin reaches apredetermined full quantity, the stored ice detector SI detects it andopens.

A relay coil Rw constitutes a relay together with a relay switch W1, anormally open type relay switch W2, a normally closed type relay switchW3 and a normally open type relay switch W4. This relay coil Rw has oneend connected to the common lead L1 via the upper limit float switch Fuand the stored ice detector SI. The one end of the relay coil Rw isfurther connected to the common lead L1 via the lower limit float switchFl, the relay switch W2 and the stored ice detector SI. The relay coilRw has the other end connected to the common lead L2. The relay coil Rwis energized to close the individual relay switches W1, W2 and W4 andopen the relay switch W3 when the upper limit float switch Fu is closedwith the stored ice detector SI closed. The relay coil Rw self holds theenergization when the lower float switch Fl is closed caused by theclosing of the relay switch W2. The relay switch W3 has one endconnected to the common lead L1 via the stored ice detector SI, and hasthe other end connected to the common lead L2 via the water valve WV andboth relay switches Q3 and V4. The relay switch W3, when closed, permitsapplication of an AC voltage to the water valve WV from the common leadsL1 and L2 in order to open the water valve WV while the stored icedetector SI and both relay switches Q3 and V4 are closed. The watervalve WV is closed when the stored ice detector SI and any of the relayswitches W3, Q3 and V4 open.

A relay coil Rx constitutes a relay together with a normally open typerelay switch X, and is energized to open the relay switch X when appliedwith an AC voltage from the common leads L1 and L2. Both relay coils Rsand Ru are connected via an electronic driving circuit 140 and atransformer 130 to both common leads L1 and L2, as shown in FIGS. 3 and4. The relay coil Rs constitutes a relay together with the relay switchS1 and a normally open type relay switch S2, and closes the relayswitches S1 and S2 by its selective energization. The relay switch S2has one end connected to the common lead L1 and the other end connectedto the common lead L2 via the motor Mg of the ice making machineassembly B and an overload relay La. The relay switch S2, when closed,applies the AC voltage from the common leads L1 and L2 to the motor Mgto drive it. The overload relay La functions to cut the motor Mg fromthe common lead L2 when the motor Mg is overloaded.

The relay coil Ru constitutes a relay together with the relay switch U1and a normally open type relay switch U2, and opens the relay switch U1and closes the relay switch U2 by its selective energization. The relayswitch U2 has one end connected to the common lead L1 and the other endconnected to the common lead L2 via the compressor motor Mc and anoverload relay Lb connected in series thereto, and the fan motor Mfconnected in parallel to them. The relay switch U2, when closed, appliesan AC voltage to the compressor motor Mc and the fan motor Mf to drivethem. The overload relay Lb functions to cut the compressor motor Mcfrom the common lead L2 when the motor Mc is overloaded.

The transformer 130 transforms an AC voltage from the common leads L1and L2 and applies the resultant voltage as a low voltage to theelectronic driving circuit 140. The electronic driving circuit 140 has arectifier (not shown), which rectifies the low voltage from thetransformer 130 to a DC voltage +Vcc. The electronic driving circuit 140also has a charging circuit 140a, as shown in FIG. 4, which is chargedby a capacitor 141 in accordance with the DC voltage +Vcc coming via aresistor 141a from the rectifier. The capacitor 141 is grounded at acommon end to the resistor 141a via a resistor 141b and the relay switchW4. When the relay switch W4 is closed, this capacitor 141 spontaneouslydischarges via the resistor 141b and relay switch W4. Both inverters140b and 140c generate low-level signals in response to a charge voltagecoming via a resistor 141c from the capacitor 141 of the chargingcircuit 140a, and generate high-level signals in response to a drop ofthe charge voltage originating from the charging of the capacitor 141.

A delay circuit 140d has a capacitor 142, which is charged by theinverter 140b via a diode 142a and a resistor 142b in response to thegeneration of the high-level signal from the inverter 140b, producing afirst charge voltage. The capacitor 142 slowly discharges through aresistor 142c (having a large resistance) and the inverter 140b inresponse to the generation of the low-level signal from the inverter140b, thus lowering the first charge voltage. The delay time constant ofthe delay circuit 140d is selected to a charge time constant determinedby the forward internal resistance of the diode 142a, the resistance ofthe resistor 142b and the capacitance of the capacitor 142, i.e., 0.4sec. Accordingly, the generation of the first charge voltage from thecapacitor 142 is delayed by 0.4 sec after the generation of thehigh-level signal from the inverter 140b. In FIG. 4, the referencecharacters 141d and 142d denote reverse-flow preventing diodes.

A delay circuit 140e has a capacitor 143, which is charged by theinverter 140c via a diode 143a and a resistor 143b in response to thegeneration of the high-level signal from the inverter 140c, producing asecond charge voltage. The capacitor 143 slowly discharges through aresistor 143c (having a large resistance), the diode 143d and theinverter 140c in response to the generation of the low-level signal fromthe inverter 140c, thus dropping the second charge voltage. The delaytime constant of the delay circuit 140e is selected to a charge timeconstant determined by the forward internal resistance of the diode143a, the resistance of the resistor 143b and the capacitance of thecapacitor 143, i.e., about 60 sec. Accordingly, the generation of thesecond charge voltage from the capacitor 143 is delayed by 60 sec afterthe generation of the high-level signal from the inverter 140c. In FIG.4, the reference character 143e denotes a reverse-flow preventing diode.

A transistor 140f has its collector connected to a common end of thecapacitor 142 and diode 142d via a diode 144a, and connected to a commonend of the capacitor 143 and diode 143e via a diode 144b. Thistransistor 140f has its base grounded via a resistor 144c and both relayswitches V5 and X, and connected to the aforementioned rectifier via theresistor 144c and a resistor 144d. Therefore, the transistor 140fbecomes non-conductive when both relay switches V5 and X are closed. Thetransistor 140f becomes conductive when one of the relay switches V5 andX opens and instantaneously discharges both capacitors 142 and 143 viathe diodes 144a and 144b. In FIG. 4, the reference character 144edenotes a pull-up resistor.

A reference voltage generator 140g frequency-divides the DC voltage +Vccfrom the rectifier circuit by series-connected resistors 145a and 145band outputs this frequency-divided voltage as a first reference voltage.A reference voltage generator 140h frequency-divides the DC voltage +Vccfrom the rectifier circuit by series-connected resistors 146a and 146band outputs this frequency-divided voltage as a second referencevoltage. The first and second reference voltages are determined asvalues corresponding to the delay time constants of the delay circuits140d and 140e respectively.

A comparator 140i generates a high-level comparison signal when thefirst charge voltage from the capacitor 142 of the delay circuit 140d ishigher than the first reference voltage from the reference voltagegenerator 140g. The comparison signal from the comparator 140idisappears when the first charge voltage from the capacitor 142 is lowerthan the first reference voltage from the reference voltage generator140g. A comparator 140j generates a high-level comparison signal whenthe second charge voltage from the capacitor 143 of the delay circuit140e is higher than the second reference voltage from the referencevoltage generator 140h. The comparison signal from the comparator 140jdisappears when the second charge voltage from the capacitor 143 islower than the second reference voltage from the reference voltagegenerator 140h.

A transistor 140k is biased by resistors 147a and 147b in response tothe comparison signal from the comparator 140i to become conductive,energizing the relay coil Rs. The transistor 140k is renderednon-conductive in response to the disappearance of the comparison signalfrom the comparator 140i, deexciting the relay coil Rs. A transistor140l is biased by resistors 148a and 148b in response to the comparisonsignal from the comparator 140j to become conductive, energizing therelay coil Ru. The transistor 140l is rendered non-conductive inresponse to the disappearance of the comparison signal from thecomparator 140j, deexciting the relay coil Ru. In FIG. 4, the referencecharacters 149a and 149b denote diodes for absorbing a surge voltage.

In operation, when the AC voltage from the commercially available powersupply Ps is applied via the circuit breaker ELB between the commonleads L1 and L2 with no ice present in the aforementioned storage bin,the relay coil Rq is energized by application of the AC voltage via thestored ice detector SI to close the individual relay switches Q1, Q2 andQ3, and at the same time the relay coil Rx is energized by the ACvoltage applied via the overload relay La from the common leads L1 andL2, thereby closing the relay switch X.

When the operation switch SW is temporarily closed in the aboveconditions, the relay coil Rv is energized by application of the ACvoltage via the timer switches K and M to close the individual relayswitches V1, V2, V4 and V5 and open the relay switch V3 at the sametime, and is self-retained by the closing of the relay switch V2. Then,in accordance with the closing of the relay switch V1, the timer sectionTk is applied with the AC voltage via the individual relay switches Q1,S1 and U1, and functions to start measuring the predetermined time Dk.Further, the closing of the relay switch V4 applies the AC voltage tothe water valve WV via the stored ice detector SI and individual relayswitches W3 and Q3 to open the water valve WV. As a result, the watersource 60a starts supplying water in the water tank 60 via the watersupply pipe 61. The relay switch X, when closed, renders the transistor140f of the electronic driving circuit 140 non-conductive.

As the water in the water tank 60 increases, the float 76a of the floatswitch mechanism 70 rises to the lower limit level Ll, closing the lowerlimit float switch Fl. When the water in the water tank 60 furtherincreases to raise the float 77a to the upper limit level Lu, the upperlimit float switch Fu is closed. Consequently, the relay coil Rw isenergized by the AC voltage applied via the stored ice detector SI,thereby closing the relay switches W1, W2 and W4 and opening the relayswitch W3 at the same time. The closing of the relay switch W2 causesthe relay coil Rw to be self-retained when the lower limit float switchFl is closed.

Then, the timer section Tm operates in response to the closing of therelay switch W1 to start measuring the predetermined time Dm. The watervalve WV is closed in response to the opening of the relay switch W3,cutting off water supply to the water tank 60 from the water source 60a.This completes the supply of a predetermined quantity of water to thewater tank 60, filling the evaporator housing 20 with water. When therelay switch W4 is closed as described above, the charge circuit 140a ofthe electronic driving circuit 140 spontaneously drops the chargevoltage of the capacitor 141 to generate the high-level signals fromboth inverters 140b and 140c. Consequently, the delay circuit 140dresponds to the high-level signal from the inverter 140b with its delaytime constant to charge the capacitor 142, while the delay circuit 140eresponds to the high-level signal from the inverter 140c with its delaytime constant to charge the capacitor 143. The charge voltage of thecapacitor 142 therefore becomes higher than the reference voltage fromthe reference voltage generator 140g, and the comparator 140i generatesa comparison signal. In response to this signal, the transistor 140kbecomes conductive to energize the relay coil Rs, opening the relayswitch S1 and closing the relay switch S2 at the same time. Accordingly,the motor Mg of the ice making machine assembly B is driven by the ACvoltage applied via the relay switch S2 and overload relay La, causingthe speed reducer 10 to rotate the auger 40 in a deceleration action.

Thereafter, when the charge voltage of the capacitor 143 rises higherthan the reference voltage from the reference voltage generator 140h,the comparator 140j generates a comparison signal. In response to thissignal, the transistor 140l becomes conductive to energize the relaycoil Ru, opening the relay switch U1 and closing the relay switch U2 atthe same time. As a result, the timer section Tk stops functioning dueto the opening of the relay switch U1 with the relay switch S1 open,without opening the timer switch K. When the relay switch U2 is closedas mentioned above, the compressor motor Mc runs upon reception of theAC voltage via the overload relay Lb, so that the compressor 90 isdriven by the compressor motor Mc to start a compressing action and thecooling fan 100a is driven by the fan motor Mf to start a coolingaction. In the refrigeration cycle R, therefore, a refrigerant startscirculating, passing the compressor 90, condenser 100, receiver 110,expansion valve 120 and evaporator 30 under the cooling action of thecooling fan 100a. The cooling of water in the evaporator housing 20 bythe evaporator 30, or ice making operation by the ice making machinestarts.

In the process of such ice making operation, when the water in theevaporator housing 20 becomes flakes of ice, the ice crystals arescraped off by the helical blade 42 and are moved upward in accordancewith the rotation of the auger 40. The ice crystals are compressed in arod of hard ice by the extruding head 50, which is sequentially cut outby the cutter 53 and is retained in the storage bin after passingthrough the delivery duct 54. In the meantime, the water in the watertank 60 flows through the pipe 62 into the evaporator housing 20. Suchan ice making operation continues thereafter.

When the lower limit float switch Fl is opened after the upper floatswitch Fu opens according to a reduction of water in the water tank 60,the relay coil Rw is deenergized to open the relay switches W1, W2 andW4 and close the relay switch W3 at the same time. The opening of therelay switch W1 causes the timer section Tm to stop functioning withoutopening the timer switch M. The closing of the relay switch W3 opens thewater valve WV with both relay switches Q3 and Q4 closed to restartwater supply to the water tank 60 from the water source 60a. Thereafter,the same ice making operation as described above continues by repeatingwater supply to the water tank 60. When the stored ice detector SI opensdue to a later increase of the quantity of ice stored in the storagebin, the relay coil Rq is deenergized to open the relay switches Q1, Q2and Q3, so that the timer section Tk stops its action and the watervalve WV is kept open.

The opening of the relay switch W4 causes the charge circuit 140a of theelectronic driving circuit 140 to spontaneously charge the capacitor 141due to the deenergization of the relay coil Rw, permitting the inverters140b and 140c to generate the low-level signals. Consequently, the delaycircuit 140d instantaneously drops the charge voltage of the capacitor142 and the delay circuit 140e instantaneously drops the charge voltageof the capacitor 143. The comparators 140i and 140j therefore vanish therespective comparison signals, rendering the transistors 140k and 140lnon-conductive. Accordingly, the relay coil Ru is deenergized to closethe relay switch U1 and open the relay switch U2 at the same time.Further, the relay coil Rs is deenergized to close the relay switch S1and open the relay switch S2. Subsequently, the compressor 90 stops asthe compressor motor Mc stops, the cooling fan 100a stops by thestopping of the fan motor Mf, and the motor Mg of the ice making machineassembly B stops. This completes the ice making operation of the icemaking machine. When the stored ice detector SI is opened according toan increase in the quantity of ice stored in the storage bin, the relaycoil Rq is deenergized to open the individual relay switches Q1, Q2 andQ3, causing the timer section Tk to stop functioning and keeping thewater valve WV open. The above described operation is repeatedthereafter every time ice in the storage bin comes short.

Assume that suspension of water supply has occurred while the ice makingoperation is being carried out with the float switch mechanism 70 in theproper state in the repetition of the above-described action. When thewater level in the water tank 60 drops lower than the lower limit levelLl as the ice making operation continues, the lower limit float switchFl opens with the upper float switch Fu open. Accordingly, the relaycoil Rw is deenergized to open the relay switches W1, W2 and W4 andclose the relay switch W3. The closing of the timer switch M causes thetimer section Tm to stop functioning and the closing of the relayswitches Q3 and Q4 causes the water valve WV to start supply water tothe water tank 60 from the water source 60a, as in the above-describedcase. Like in the above case, in accordance with the opening of therelay switch W4, the relay coil Rs is deenergized to close the relayswitch S1 and open the relay switch S2 at the same time, and the relaycoil Ru is deenergized to close the relay switch U1 and open the relayswitch U2 at the same time, causing the timer section Tk to startmeasuring the time and causing the ice making machine to stop the icemaking operation.

The relay coil Rw keeps the deenergized state without closing the upperlimit float switch Fu due to suspension of water supply. When the timersection Tk opens the timer switch K upon completion of the timemeasurement, the relay coil Rv is deenergized to open the relay switchesV1, V2, V4 and V5 and close the relay switch V3 at the same time. Then,the timer section Tk stops functioning to close the timer switch K inresponse to the opening of the relay switch V1, the timer section Tnfunctions to start measuring the predetermined time Dna in response tothe opening of the relay switch V1 with the relay switch Q2 closed, thewater valve WV is closed by the opening of the relay switch V4, and thetransistor 140f, when the relay switch V5 is open, is biased to beconductive by the resistors 144d and 144c based on the DC voltage of theaforementioned rectifier, spontaneously discharging the capacitors 142and 143 through the respective diodes 144a and 144b. The comparators140i and 140j therefore vanish the comparison signals to render thetransistors 140k and 140l non-conductive, deexciting the relay coils Rsand Ru. The opening of the relay switch S2 stops the motor Mg and theopening of the relay switch U2 stops the compressor motor Mc and fanmotor Mf.

When the predetermined time Dna is elapsed, the timer section Tn closesthe timer switch N and starts measuring the predetermined time Dnb asthe measuring of the predetermined time Dna has completed. When thepredetermined time Dnb is elapsed next, the timer section Tn opens thetimer switch N and starts measuring the predetermined time Dna as themeasuring of the predetermined time Dnb has completed. Thereafter, thetimer section Tn in action repeats the aforementioned operation.

While the timer section Tn is measuring the predetermined time Dnarepetitively, the relay coil Ry is energized by an AC voltage appliedevery time the timer switch N is closed with the relay switch Q2 closed,thereby closing the relay switches Y1 and Y2. Therefore, the relay coilRv is energized every time the relay switch Y1 is closed with both timerswitches K and M closed, thereby closing the relay switches V1, V2, V4and V5 and opening the relay switch V3. With the relay switches W3 andQ3 closed, the water valve WV is open in response to each closing of therelay switch V4. With the relay switches Q1, S1 and U1 closed, the timersection Tk starts measuring the predetermined time Dk in response to theclosing of the relay switch V1, and, upon completion of the timemeasurement, opens the timer switch K to deenergize the relay coil Rv,thus closing the water valve WV. The relay coil Rv self retains theenergization caused by the closing of the relay switch Y1 while thetimer switch K and relay switch V2 are both closed. The state of thetime measurement of the timer section Tn which has started by theclosing of the relay switch Y2 is kept by the closing of the relayswitch Y2 irrespective of the opening of the relay switch V3.

When suspension of water supply is cleared during such repetition of theopening/closing action of the water valve WV, water supply from thewater source 60a to the water tank 60 is started upon opening of thewater valve WV. Thereafter, when the upper limit float switch Fu isclosed after closing of the lower limit float switch Fl according to anincrease of water in the water tank 60, the relay coil Rw is energizedto close the relay switches W1, W2 and W4 and open the relay switch W3.Like in the above-described case, the water valve WV is closed and theice making machine starts the ice making operation.

As describe above, when suspension of water supply occurs, the watervalve WV is repeatedly kept open during passing of the predeterminedtime Dk every time the predetermined time Dna elapses by the interactionof the timer sections Tk and Tn, the timer switches K and N, the relaycoils Ry and Rv and the individual relay switches Y1, Y2, V1, V2 and V4.As suspension of water supply is cleared, therefore, water supply to thewater tank 60 and the ice making operation of the ice making machine areautomatically executed in order. In this case, during the time perioduntil clearing of the suspension of water supply, the water valve WV isopened while each predetermined time is measured, i.e., for the timerequired to supply water to the water tank 60, thus minimizing the powerconsumption needed to open the water valve WV.

When opening of the upper limit float switch Fu is disabled by contactmelting due to an excess current flowing in the reed switch 79 in therepetition of the above-described action, the relay coil Rw is keptenergized to maintain the closing of the relay switches W1, W2 and W4and the opening of the relay switches W3 as long as the stored icedetector SI is closed based on insufficient ice in the storage bin. Asshould be understood from the above explanation of the action, theopening of the relay switch W3 does not allow the water valve WV to beopen, disabling water supply from the water source 60a into the watertank 60. Also, as should be understood from the above explanation of theaction, the closing of the relay switch W4 holds the relay coils Rs andRu energized to keep activating the motor Mg, compressor motor Mc andfan motor Mf.

Although water in the water tank 60 and evaporator housing 20 comesshort, therefore, the evaporator 30 keeps cooling the evaporator housing20 under the action of the compressor 90, and the auger 40 is keptfunctional by the motor Mg. Since the timer section Tm opens the timerswitch M when the predetermined time Dm elapses after the closing of therelay switch W1, however, the relay coil Rv is deenergized, opening therelay switch V5. The transistor 140f is therefore biased to beconductive by the resistors 144d and 144c based on the DC voltage of therectifier, spontaneously discharging the capacitors 142 and 143 via therespective diodes 144a and 144b. The comparators 140i and 140j thereforevanish the comparison signals to render the transistors 140k and 140lnon-conductive, deexciting the relay coils Rs and Ru. The opening of therelay switch S2 stops the motor Mg and the opening of the relay switchU2 stops the compressor motor Mc and fan motor Mf.

As described above, even with the opening of the upper limit floatswitch Fu disabled, the relay coils Rs and Ru are deenergized toimmediately stop the ice making operation of the ice-making machine bythe opening of the timer switch M upon completion of time measurement inthe timer section Tm after the relay switch W1 has been closed. It istherefore possible to hinder over cooling of the evaporator housing 20due to water shortage, thereby preventing over ice forming in theevaporator housing 20. The compressor 90, motor Mg, speed reducer 10 andauger 40 can therefore keep their inherent service lives without beingoverloaded due to over cooling or over ice forming. The above can betrue of the case where opening of the lower limit float switch Fl isdisabled by contact melting due to an excess current flowing in the reedswitch 78. In the case where the refrigerant of the refrigerationcircuit R leaks outside even when the upper limit float switch Fu andlower limit float switch Fl are normal, the ice making operation stopsupon completion of time measurement by the timer section Tm in the samemanner as described above, countermeasure to the refrigerant leakage canquickly be taken.

In the case where closing of the upper limit float switch Fu is disableddue to dust or the like entering together with water in the water tank60 and present between the stopper 75 and float 77 of the float switchmechanism 70, the upper limit float switch Fu cannot be closed even whenthe level of water in the water tank 60 rises to the upper limit levelLu, as described above. Accordingly, the relay coil Rw, whendeenergized, keeps the relay switches W1, W2 and W4 open and the relayswitch W3 closed. As described above, therefore, the opening of thewater valve WV with the relay switches W3, Q3 and V4 closed keeps watersupply from the water source 60a into the water tank 60.

When the timer switch K is opened in response to the completion of timemeasurement of the timer section Tk after the relay switch V1 is closed,however, the relay coil Rv is deenergized to open the relay switches V1,V2, V4 and V5 and close the relay switch V3. The opening of the relayswitch V4 immediately closes the water valve WV, inhibiting water supplyfrom the water source 60a to the water tank 60. As a result, watersupply to the water tank 60 will not be done unnecessarily even when theclosing of the upper limit float switch Fu is disabled, thus preventingwasting of water and protecting the vicinity of the location of the icemaking machine from being flooded with water due to water discharge fromthe water tank 60.

When closing of the lower limit float switch Fl is disabled due to theaforementioned dust or the like, this float switch Fl is always openirrespective of a variation in the quantity of water in the water tank60. When the closing of the upper limit float switch Fu energizes therelay coil Rw to close the relay switches W1, W2 and W4 and open therelay switch W3, as described above, the water valve WV is closed by theopening of the relay switch W3, stopping water supply from the watersource 60a to the water tank 60, and the electronic driving circuit 140starts the action of the ice making machine assembly B and the icemaking operation by the closing of the relay switch W4.

In this case, although the upper limit float switch Fu is open inaccordance with a decrease of water in the water tank 60, the lowerlimit float switch Fl is open so that the relay coil Rw is deenergizedimmediately after the opening of the float switch Fu, thus closing therelay switch W3. Although there is a sufficient quantity of water in thewater tank 60, therefore, water is supplied from the water source 60ainto the water tank 60 by the opening of the water valve WV. This meansthat repetitive opening/closing of the upper limit float switch Furepeats the opening/closing of the water valve WV.

As described above, however, in accordance with the completion of timemeasurement by the timer section Tk after the relay switch V1 is closed,the relay coil Rv is deenergized by the opening of the timer switch K,thus opening the relay switches V4 and V5. The opening of the relayswitch V4 closes the water valve WV and the opening of the relay switchV5 causes the electronic driving circuit 140 to deenergize the relaycoils Ru and Rs, stopping the ice making operation and the action of theauger 40 as in the above-described case. In this case, the opening ofthe relay switch V4 minimizes the frequency of opening/closing of thewater valve WV to ensure its service life.

When power failure occurs while the ice making machine is executing theice making operation with the float switch mechanism in the propercondition, for example, the ice making machine stops the ice makingoperation as the individual electric components stop functioning. Inthis case, after recovery of power failure causes the relay coil Rq tobe energized to close the relay switches Q1 and Q2, the timer section Tnstarts measuring the time by the closing of the relay switch Q2, so thatthe ice making operation of the ice making machine is automaticallyperformed in substantially the same manner as in the case of suspensionof water supply.

When a normally closed type relay switch W6 is connected in series tothe relay switch Q1 as shown in FIG. 5, in place of the parallel circuitof the relay switches S1 and U1 in the above embodiment, the timemeasuring action of the timer section Tk is allowed when the relayswitch W6 is closed based on the deenergization of the relay coil Rw. Atthe time closing of the upper limit float switch Fu is disabled,therefore, the timer section Tk opens the timer switch K without openingthe relay switch W6 when completing measuring the time. Therefore, theopening of the relay switches V1, V2, V4 and V5 originating from thedeenergization of the relay coil Rv inhibits the water supply of thewater valve WV and the ice making operation in the same manner asdescribed above, thus accomplishing the same advantage associated withthe disabled closing of the upper limit float switch Fu as obtained inthe above embodiment.

FIG. 6 illustrates a modification of the aforementioned control circuitE. In this modification, the timer section Tn, its control circuit andthe relay switches Y1 and Y2, which constitute a relay together with therelay coil Ry, shown in FIG. 3, are omitted, so that when the opening orclosing of the upper limit float switch Fu or lower limit float switchFl is disabled, the motor Mg, compressor Mc and fan motor Mf stopfunctioning upon elapse of the predetermined time Dm under the controlof the timer section Tm. As the other structure and operation are thesame as those of the aforementioned control circuit E, their descriptionwill not be given.

FIG. 7 illustrates another embodiment of the control circuit E. Thecontrol circuit Ea in this embodiment has a timer section Td, whichconstitutes a timer together with normally closed type timer switches D1and D2. This timer section Td has one end connected to the common leadL2 and the other end connected to the common lead L1 through a normallyclosed type time-limit switch ZA1 and a normally open type relay switchZB1 connected together in series and a parallel circuit of a normallyopen type time-limit switch ZA2 and a normally closed type relay switchZB3. Accordingly, the timer section Td functions to measure apredetermined time Dd when applied with an AC voltage with either thetime-limit switch ZA2 or the relay switch ZB3 closed, or the time-limitswitch ZA1 and relay switch ZB1 both closed. Then, the timer section Tdopens both timer switches D1 and D2 upon completion of the timemeasurement and cuts the timer switches D1 and D2 from the AC voltagefrom the common leads L1 and L2 to close the timer switches D1 and D2.The timer switch D1 has one end connected to the common lead L2 and theother end connected to the common lead L1 via the water valve WV and thenormally closed type relay switch Y1. The water valve WV is thereforeopened or closed by the closing or opening of the timer switch D1 withthe relay switch Y1 closed. The predetermined time Dd corresponds to 1.2to 1.5 times the time needed to form water supplied to the upper limitlevel Lu in the water tank 60 into ice.

The relay coil Ry constitutes a relay together with the relay switchesY1 and Y2, and a normally open type relay switch Y3. This relay coil Ryhas one end connected to the common lead L1 via a parallel circuit ofthe normally open type relay switches Y2 and ZA3, and has the other endconnected to the common lead L2 via the normally open type relay switchZB2 and the timer switch D2. When applied with the AC voltage with therelay switches Y2, ZA3 and ZB2 and a timer switch Q2 closed, the relaycoil Ry is energized to open the relay switch Y1 and close the relayswitches Y2 and Y3. The relay switch Y3 has one end grounded via thestored ice detector SI and the other end connected to the resistor 141b,as shown in FIGS. 7 and 8.

A relay coil Rza constitutes a delay relay together with the time-limitswitches ZA1 and ZA2 and the relay switch ZA3. This relay coil Rza hasone end connected to the common lead L2 and the other end connected tothe common lead L1 via the upper limit float switch Fu. The relay coilRza is therefore energized by the AC voltage applied under closing ofthe upper limit float switch Fu, and thus opens the time-limit switchZA1 with a delay and close the time-limit switch ZA2 and relay switchZA3. When the relay coil Rza is deenergized, the time-limit switch ZA1is instantaneously closed, the time-limit switch ZA2 is opened with adelay, and the relay switch ZA3 is opened spontaneously.

A relay coil Rzb constitutes a relay together with the relay switchesZB1, ZB2 and ZB3. This relay coil Rzb has one end connected to thecommon lead L2 and the other end connected to the common lead L1 via thelower limit float switch Fl. The relay coil Rzb is therefore energizedby the AC voltage applied when the lower limit float switch Fl isclosed, and closes the relay switches ZB1 and ZB2 while opening therelay switch ZB3.

In operation of the control circuit Ea, when an AC voltage is appliedbetween the common leads L1 and L2 from the commercially available powersupply Ps, the water valve WV is opened to supply water into the watertank 60 from the water source 60a. At this time, the relay coil Rx isenergized to close the relay switch X, thereby rendering the transistor140f non-conductive.

When the lower limit float switch Fl is closed due to an increase ofwater in the water tank 60, the relay coil Rzb is energized to close therelay switches ZB1 and ZB2 while opening the relay switch ZB3. Then, thetimer section Td functions to start measuring the predetermined time Ddin response to the closing of the relay switch ZB1 with the relay switchZA1 closed. Further, when the upper limit float switch Fu is closed dueto an increase of water in the water tank 60, the relay coil Rza isenergized to open the time-limit switch ZA1 with a delay andspontaneously close the time-limit switch ZA2 and the relay switch ZA3.The timer section Td therefore keeps measuring the time when thetime-limit switch ZA2 is closed with the time-limit switch ZA1 openedwith a delay. The relay coil Ry is energized to open the relay switch Y1and close the relay switches Y2 and Y3 in response to the closing of therelay switch ZA3 with the relay switch ZB2 and time switch D2 bothclosed, and is self-retained by the closing of the relay switch Y2.

When the relay switch Y1 is opened as described above, the water valveWV is closed to stop supplying water to the water tank 60 from the watersource 60a. Further, the electronic driving circuit 140 drives the auger40 and compressor 90 by means of energization of the relay coils Rs andRu when the relay switch Y3 is closed with the stored ice detector SIclosed. After water supply to the water tank 60 is completed, therefore,the ice making machine starts its ice making operation.

When the upper limit float switch Fu is opened as the ice makingoperation progresses, the relay coil Rza is deenergized to spontaneouslyclose the time-limit switch ZA1 and open the time-limit switch ZA2 witha delay as well as open the relay switch ZA3. At this time, the timersection Td continues the time measurement based on the delayed openingof the time-limit switch ZA2 and the spontaneous closing of thetime-limit switch ZA1. When the lower limit float switch Fl is openedthereafter, the relay coil Rzb is deenergized to open both the relayswitches ZB1 and ZB2. The opening of the relay switch ZB1 causes thetimer section Td to stop functioning without opening both timer switchesD1 and D2. The opening of the relay switch ZB2 deenergizes the relaycoil Ry, closing the relay switch Y1 and opening the relay switches Y2and Y3.

The closing of the relay switch Y1 opens the water valve WV to supplywater to the water tank 60 from the water source 60a, and the electronicdriving circuit stops the ice making operation by deenergization of therelay coils Rs and Ru in response to the opening of the relay switch Y3.The ice making operation and water supply to the water tank 60 arerepeated thereafter in the same manner as described above. When thestored ice detector SI is opened later in accordance with an increase inthe quantity of ice in the storage bin with the relay switch Y3 closed,the electronic driving circuit 140 completes the ice making operation bydeenergization of the relay coils Rs and Ru. The above-described actionwill be repeated every time ice in the storage bin becomes short.

When the opening of the upper limit float switch Fu is disabled in therepetition of the above-described action, the relay coil Rza, whenenergized, keeps the time-limit switch ZA1 open and the time-limitswitch ZA2 and the relay switch ZA3 closed. As the relay switch Y1 isopened, therefore, the water valve WV cannot be opened, disabling watersupply to the water tank 60. As long as the stored ice detector SI isclosed, the relay coils Rs and Ru are kept energized by the closing ofthe relay switch Y3, permitting the ice making operation to continue.This means that the ice making machine continues the ice makingoperation even when water in the water tank 60 comes short.

Since the timer section Td opens both timer switches D1 and D2 uponelapse of the predetermined time Dd after the time-limit switch ZB1 isclosed, however, the relay coil Ry is deenergized by the opening of thetimer switch D2 to close the relay switch Y1 and open the relay switchesY2 and Y3. The electronic driving circuit 140 therefore stops the icemaking operation in response to the opening of the relay switch Y3. Atthis time, the water valve WV is closed with the timer switch D1 opened,regardless of the closing of the relay switch Y1.

As described above, even if the opening of the upper limit float switchFu is disabled, the relay coils Rs and Ru are deenergized to immediatelystop the ice making operation of the ice making machine by the openingof the timer switch D2, which is originated from the termination of timemeasurement in the timer section Td after the time-limit switch ZB1 isclosed. The above is also true of the case when the opening of the lowerlimit float switch Fl is disabled.

With the closing of the upper limit float switch Fu disabled, even whenthe level of water in the water tank 60 rises to the upper limit levelLu, the relay coil Rza will not be energized, keeping the time-limitswitch ZA1 closed and the time-limit switch ZA2 and relay switch ZA3opened. Accordingly, the closing of the relay switch Y1 keeps watersupply from the water source 60a to the water tank 60 via the watervalve WV.

When the timer switch D1 is opened due to the completion of the timemeasurement in the timer section Td after the relay switch ZB1 isclosed, however, the water valve WV is closed to immediately inhibitwater supply to the water tank 60 from the water source 60a.

With the closing of the lower limit float switch Fl disabled, even whenthe upper limit float switch Fu is closed according to water supply tothe water tank 60, the closing of the relay switch Y1 permits watersupply from the water source 60a to the water tank 60 to continue.

After the relay coil Rza, when energized by the closing of the upperlimit float switch Fu, closes the time-limit switch ZA2, however, thetimer section Td completes measuring the time with the relay switch ZB3closed, thus opening the timer switch D1. This closes the water valve WVto inhibit water supply to the water tank 60. It is therefore possibleto prevent water from being wasted and protect the vicinity of thelocation of the ice making machine from being flooded with water.

FIGS. 9 and 10 illustrate a modification of the control circuit Ea. Inthis modification, a relay coil Rzc which constitutes a relay togetherwith a normally open type relay switch ZC1 has one end connected via thestored ice detector SI to the common lead L1, and has the other endconnected via the timer switch D1 to the common lead L2. The relay coilRzc is therefore energized by an AC voltage applied when the stored icedetector SI and timer switch D1 are both closed, thereby closing therelay switch ZC1. The relay switch ZC1 has one end grounded and theother end connected to the relay switch Y3. The timer switch D2 isomitted.

In operation of the modification, when an AC voltage is applied betweenthe common leads L1 and L2 from the commercially available power supplyPs, the relay coil Rzc is energized to thereby close the relay switchZC1 with the stored ice detector SI and timer switch D1 both closed.When the relay switch Y3 is closed thereafter, the electronic drivingcircuit 140 permits the ice making machine to carry out the ice makingoperation by energization of the relay coils Rs and Ru. When the storedice detector SI is opened upon completion of the ice making operation,the relay coil Rzc is deenergized to open the relay switch ZC1. Theelectronic driving circuit 140 therefore stops the ice making operationby deenergization of the relay coils Rs and Ru. With the closing of theupper limit float switch Fu or lower limit float switch Fl disabled,when the timer section Td opens the timer switch D1 upon completion ofthe time measurement after the time-limit switch ZA2 or relay switch ZB1is closed, the water valve WV is closed to stop supplying water to thewater tank 60. At the same time, the relay coil Rzc is deenergized toopen the relay switch ZC1, causing the electronic driving circuit 140 tostop the ice making operation.

We claim:
 1. An electric control apparatus for an auger type ice makingmachine having a water tank for supplying water connected to anevaporator housing incorporating an auger rotatable by an electric motorand having an evaporator provided on an outer wall thereof, a compressorconnected to the evaporator, a water tank arranged to supply fresh watertherefrom into the evaporator housing, and a solenoid water valvedisposed within a water supply pipe connecting the water tank to asource of water, to thereby permit supply fresh water into the tank whenthe solenoid water valve is opened by energization thereof, the electriccontrol apparatus comprising:a first float switch for detecting thelevel of water in the water tank to be actuated when the water leveldrops below a lower limit; a second float switch for detecting the levelof water in the water tank to be actuated when the water level reachesan upper limit; a first control means for, when the first float switchis actuated, opening the solenoid water valve by energization thereofand cutting off power supply to the electric motor and the compressor; asecond control means for, when the second float switch is actuated afterthe first float switch is actuated in accordance with an increase ofwater in the water tank, closing the solenoid water valve bydeenergization thereof and then permitting power supply to the electricmotor and the compressor; a first timer means for, when the first floatswitch is actuated, starting measurement of a first control time setlonger by a predetermined time than a time for the level of water in thewater tank to reach the upper limit from the lower limit; and a thirdcontrol means for closing the solenoid water valve by deenergizationthereof when the measurement of the first control time terminates in acondition where the first float switch is not switched due to suspensionof water supply.
 2. An electric control apparatus as claimed in claim 1,further comprising:a second timer means for sequentially and repeatedlymeasuring a predetermined second control time and a predetermined thirdcontrol time when the solenoid water valve is closed by deenergizationthereof under control of the third control means; and a fourth controlmeans for energizing the solenoid water valve while the second controltime is being measured by the second timer means and for deenergizingthe solenoid water valve while the third control time is being measuredby the second timer means.
 3. An electric control apparatus as claimedin claim 1, further comprising:a second time means for, when the secondfloat switch is actuated, starting measurement of a second control timecorresponding to a time for the level of water in the water tank to dropbelow the lower limit from the upper limit; and a fourth control meansfor cutting off power supply to the electric motor and compressor whenthe measurement of the second control time terminates in a conditionwhere the first float switch is not actuated in accordance with adecrease of water in the water tank.
 4. An electric control apparatus asclaimed in claim 3, further comprising:a fifth control means for closingthe solenoid water valve by deenergization thereof when the measurementof the first control time terminates in a condition where the secondfloat switch is not actuated in accordance with an increase of water inthe water tank and for cutting off power supply to the electric motorand compressor when the measurement of the second control timeterminates in a condition where the second float switch is not switchedin accordance with a decrease of water in the water tank.
 5. An electriccontrol apparatus for an auger type ice making machine having a watertank for supplying water connected to an evaporator housingincorporating an auger rotatable by an electric motor and having anevaporator provided on an outer wall thereof, a compressor connected tothe evaporator, a water tank arranged to supply fresh water therefrominto the evaporator housing, and a solenoid water valve disposed withina water supply pipe connecting the water tank to a source of water, tothereby permit supply fresh water into the tank when the solenoid watervalve is opened by energization thereof, the electric control apparatuscomprising:a first float switch for detecting the level of water in thewater tank to be actuated when the water level drops below a lowerlimit; a second float switch for detecting the level of water in thewater tank to be actuated when the water level reaches an upper limit; afirst control means for, when the first float switch is actuated,opening the solenoid water valve by energization thereof and cutting offpower supply to the electric motor and the compressor; a second controlmeans for, when the second float switch is actuated after the firstfloat switch is actuated in accordance with an increase of water in thewater tank, closing the solenoid water valve by deenergization thereofand then permitting power supply to the electric motor and thecompressor; a timer means for, when the second float switch is actuated,starting measurement of a control time corresponding to a time for thelevel of water in the water tank to drop from the upper limit to thelower limit; and a third control means for cutting off power supply tothe electric motor and compressor when the measurement of the controltime terminates in a condition where the first float switch is notactuated due to malfunction thereof in accordance with a decrease ofwater in the water tank.